Polyamide-polyphenylene ether based materials are employed for various uses, particularly, uses for vehicles, such as body panels, fuel flappers, door mirror shells, wheel caps, blower fans for air conditioners, and relay blocks because of their excellent mechanical characteristics, heat resistance, oil resistance, etc. These component parts are required to maintain stable characteristics over a wide temperature range. Therefore, they are required to have excellent mechanical characteristics and discoloration resistance after hot aging and high impact strength at low temperatures.
As for the technologies for increasing mechanical strength after hot aging, for example, Patent Document 1 and Patent Document 2 disclose addition of a copper compound. However, these technologies can improve mechanical characteristics and the like after hot aging, but suffer from the problems that the molded pieces after hot aging seriously discolor to result in restrictions in uses and colors.
Furthermore, as for the technologies for improving discoloration resistance, for example, Patent Documents 3-5 disclose addition of titanium dioxide. However, these technologies are mainly for inhibition of light discoloration of polyamide-polyphenylene ether based materials and are not so effective for inhibition of discoloration caused by exposure to high temperatures as mentioned above. Some effects are recognized in the case of adding titanium dioxide in a large amount, but in this case mechanical characteristics are deteriorated, which does not meet the requirement of high mechanical strength after hot aging demanded by the market.
As a technology of enhancing multi axial impact strength of polyamide-polyphenylene ether based materials, for example, Patent Document 6 discloses to melt kneading a block copolymer having a specific viscosity at a specific temperature to form a network structure of the block copolymer. Furthermore, Patent Document 7 discloses a technology in which polyphenylene ether particles are dispersed so that more than half of the dispersed particles have a dispersion diameter of 1.0 μm or less, and, furthermore, concentration of terminal groups of polyamide and polyphenylene ether is limited to a specific range. However, it has recently been found that the above technology is insufficient for improving the practical multi axial impact strength. That is, the resin composition obtained by the above technology is improved in multi axial impact strength of its molded articles in the form of flat plate, but is not sufficiently improved for practically usable molded articles having a three-dimensional shape. For example, the molded articles used for vehicles, such as body panels, fuel flappers, door mirror shells, wheel caps and blower fans for air-conditioners, all have a curved surface. That is, the performance demanded for polyamide-polyphenylene ether based materials by the market is high multi axial impact strength of the curved surface portions at low temperatures.
Usually, polyamide-polyphenylene ether based materials have a relatively high standard deviation in measurement of multi axial impact strength of flat plate molded pieces at low temperatures (namely, having a relatively great variation in multi axial impact strength at low temperatures). Even in the case of a composition having a sufficient multi axial impact strength in its flat plate molded pieces, there is a problem that variation is apt to be caused in multi axial impact strength of curved surface portions of the molded pieces at low temperatures as compared with multi axial impact strength of flat plate molded pieces, resulting in decrease of the average value. That is, it is clear that in order to improve the multi axial impact strength of curved surface portions of the molded pieces, there are needed resin compositions capable of providing flat plate molded pieces having a more stable multi axial impact strength at low temperatures with no variation.
Moreover, there is a problem that since large molding machines of the several thousand-ton class in mold clamping pressure are used for making large molded articles such as body panels, fuel flappers and door mirror shells of automobiles, residence time of the resin in the cylinder of the molding machines increases, resulting in sharp reduction of mechanical characteristics (particularly, impact resistance). For attaining the stability after retention of resin in these molding machines, the above-mentioned technologies are insufficient and improvement in this respect has been demanded.
Patent Document 1: U.S. Pat. No. 4,857,575
Patent Document 2: JP-A-6-157894
Patent Document 3: JP-A-5-306368
Patent Document 4: JP-A-5-295250
Patent Document 5: JP-A-6-287446
Patent Document 6: JP-A-63-92668
Patent Document 7: JP-A-2002-338805